1. Field of the Invention
The invention relates to slide fasteners, and particularly to slide fasteners employing coupling elements which are joined in a train by being molded around connecting threads and to methods and apparatus for manufacture of such slide fasteners.
2. Description of the Prior Art
The prior art, as exemplified in U.S. Pat. Nos. 3,328,857; 3,414,948; 3,445,915; 3,487,531; and 3,490,111, contains a number of slide fasteners employing continuous molded coupling elements with embedded connecting threads. The continuous molded coupling elements are formed by injecting molten thermoplastic resin into transverse elongated cavities in a periphery of a cavity wheel having annular grooves for receiving the connecting threads intersecting the cavities. The molded coupling elements are then bent into a U-shape and the leg portions thereof are secured to a tape by stitches, warp threads of a woven tape, or the like. Using the connecting threads to secure the prior art coupling elements to tapes such as by the weft threads of woven tapes, generally results in inferior slide fasteners due to a weakness of the union between the coupling elements and the connecting threads, a weakness of the connecting threads, or other deficiency.